Isaiah Gregory, of Carol Place, was arrested yesterday on charges he opened fire outside of the United Artists All-Staten Island Stadium theater on Forest Avenue in Mariners Harbor on Feb. 20. The shooting happened at about 11:15 p.m., just as a throng of moviegoers were leaving their Friday night showings.

Gregory also hit a teenager who authorities believe was his intended target, striking him once in the leg, police allege.

The motive for the shooting remains unclear -- the victim isn't cooperating with the investigation, a law enforcement source said, and Gregory made no statements to detectives. An eyewitness at the crowded theater helped police identify Gregory, the source said.

Gregory faces charges of first-degree assault, second-degree criminal possession of a weapon, second-degree criminal use of a firearm, and first-degree reckless endangerment. He's scheduled to be arraigned in Stapleton Criminal Court this afternoon.